muirhead



2 Sheets-Sheet 1.

(No Model.)

A. MU'IRHBAD.

DUPLEX AND QUADRUPLEX TELBG-RAPHY.

Patented July 3, 1883.

IJV'V'EJVZOR .fllexwzder Muir/lead, By his Attorneys (No Model.) 2 Sheets-Sheet 2.

N -A. MUIRHBAD.

DUPLEX AND QUADRUPLEX TBLEGRAPHY.

No. 280,753. Patented July 3, 1883.

W49, fizz ufillexaildel'fluirkead,

By his Attorneys Q1 WWW N. Pn'zns. Pbololmgnphlr, Washingion, 07c.

PATENT OFFICE.

ALEXANDER MUIRHEAD,

OF LONDON, ENGLAND.

DUPLEX AND QUADRUPLE X TELEGRAPHY.

SP 01? FICATION forming part of Letters Patent No. 280,753, dated July 3, 1883.

Application filed November 27; 1882. g (No model.)

To all whom it may concern;

Be it known that I, ALEXANDER MUIRHEAD, a subject of the Queen of Great Britain, residing in London, England, have invented certain new and useful Improvements in Duplex and Quadruplex Telegraphy, of which the following is a specification.

My invention relates to v certain improvements in the construction and arrangement of apparatus and circuits for multiple-telegraph systems. 7

Serious hinderances to the successful operation of multiple telegraphs have heretofore been encountered, which have been due to the effect upon receiving-instruments of electrostatic charges and discharges passing to and from the lines. Various means have been devised and methods adopted in order to counteract these effects and to eliminate or reduce their causes. These methods, for the most part, depend upon the employment of an artificial or equating line having a resistance approximately equal to that of the main or actual line, and which is arranged to be charged and discharged simultaneously therewith, the design being to oppose the static effects of the artificial to those of the main line, and thus cause them to neutralize the effect of each other upon the receiving instruments. In practice, however, it has been found that although the resistances of the main and artificial lines may be equal, yet, owing to the fact that while the one consists of a long line of high degree of conductivity, the rate with which permanent currents from a given electro-motive force establish themselves in the two will differ materially. From this difference in the rates of charging and discharging it results that when batteries of equal electro-motive force are simultaneously connected with the main and artificial lines the electrical potential at the terminal of the mainline, which has thus been attached to the battery, falls below the normal potential of the latter with a rapi dity dependent upon the rapidity with which the current flows into the uncharged conductor beyond. In like manner the fall of potential of the connected terminal of the artificial'line depends upon the rapidity of the outflow of the current through that conductor. Hence the potential of the transmitting terminals of the respective lines will continue to'be unequal until both lines become fully charged, or until the rapidity of the outflow upon the two lines has been rendered equal. In certain systems of multiple telegraphy this diiferenceinpotential reacts upon the receiving-instruments at the transmitting-stati on, rendering the operation of simultaneously transmitting and receiving over a single conductor exceedingly difficult.

The object of my invention is to so organize and arrange the circuits in amultiple-tele graph system, in which currents are simultaneously transmitted from batteries or bat tery-sections of equal electro motive force through a main and an artificial line, that the potentials at the respective transmitting terminals shall be rendered approximately equal at all times, and to so arrange the apparatus at the respective terminals of the main line that currents possessing the necessary characteristics for the various classes of multiple telegraphy may be readily transmitted and received.

To this end my invention consists in com- 'bining with a main and artificial line a series of batteries or batterysections and means for simultaneously placing equal portions thereof in electrical connection with the main and artificial lines, respectively, and means for maintaining the potential of the transmitting terminals of the two lines approximately equal. These may consist either of a shunt-circuit of considerable resistance around the portion of the battery connected with the artificial line, within which shunt is included an adjustable inductor consisting of a coil of insulated wire surrounding a soft-iron bar, by means of which the rapidity with which an electric current is allowed to flow from the connected terminal of the battery may be accurately adjusted; or' of a shunt around the portion of the battery connected with the main line, in which is includ ed a condenser the charge of which will be liberated simultaneously with the transmission of each impulse or signal, and will thus serve to maintain the potential at the terminal of the battery transmitting the impulse upon the main line at the same point as that of the battery momentarily connected with the artificial line.

The invention also comprises certain details in the construction and arrangement of the ap paratus, hereinafter fully set forth.

I11 the accompanying drawings, Figure 1 is a diagram illustrating my invention as ap plied to quadruplex telegraphy, and Fig. 2 illustrates a convenient method of constructing the adjustable inductor shown in Fig. 1. Fig. 3 is a diagram exhibiting certain modifications in the application of the invention.

Referring to the diagram, L represents the main line or conductor of a telegraphic system, and Z an artificial line in which is included an artificial resistance, X, approximately equal to that of the main line.

K and K represent two independent keys or equivalent devices for transmitting through the main line L and the artificial line Z currents of different strengths derived from a series of batteries, 0 O O and 0 0 0 The key K consists of a lever, 7.1, pivoted at a, and extending between two insulated contact-springs, a and b. Two contact-points, c and d, are car ried at the extremity of the lever is, for placing the same in electrical connection with one or the other of the springs a and b, according as the key is raised or depressed.

Between the springs a and b is placed an insulated resting contact stop, 0, with which the springs a I) make contact when not pressed away by the key-lever 7c.

The transmitting device K is precisely similar in mechanical construction to the key K, consisting of a lever, is, contact-springs a b, contact-points c d, and resting-contact e.

The batteries 0 and 0 consist of an equal number of cells, or possess equal electro-motive forces, and they respectively have one pole of opposite denominations connected with the main and artificial lines L and Z. Thus the battery 0 has its positive pole connected by a wire, 1, with the main line L, and the bat tery 0 its negative pole connected by a wire, 2, with the artificial line I. The remaining poles of the two batteries are respectively connected by the wires 3 and at with the key-lever I; and resting-contact c.

The batteries 0 and 0' which are each as sumed to have an eleetro-motive force twothirds as great as that of the batteries 0 and 0, respectively, are connected as follows: The battery 0 has its negative pole connected by a wire, 5, with the contact-spring b of the key K, and its negative pole by a wire, 7 with the key-lever Zc of the key K. The battery 0 has its positive pole connected by a wire, 6, with the remaining contact-spring a of the key K, and its negative pole by a wire, 8, with the resting-contact e of the key K.

The batteries 0 and 0 are each assumed to have one-half the electro-motive force of the batteries 0 or 0'-, or one-third that of the batteries O or 0. The battery 0 has its negative pole connected by a wire, 9, with the contact-spring I) of the key K and its positive pole with the earth at G through wires 11 and 13. The positive pole of the battery 0 is 0011- nected by a wire, 10, with the remaining contact-spring a of the key K and the negative pole by wires 12 and 13 with the earth at G.

It is evident that when the keys K and K are in their normal position, as shown in the diagram, the negative pole of battery 0 will beconnected, through wire 3, key-lever in, contact-point cl, contact-spring b, and wire 5, with the negative pole of the battery 0. The positive pole of this battery 0" is normally con nected, through wire 7, key-lever k, contactpoint (1, contactspring I), and wire 9, with the negative pole of the battery 0. The positive pole of the battery 0 is connected, as already described, with the earth at G. The two batteries 0" and 0, having a combined electro-motive force equal to that of the bat tery O and opposed thereto, transmit no current to the line L. In like manner the batteries 0* and 0" are normally opposed to the battery 0, the latter having its positive pole connected, through wire 4, resting-contact c, and spring a, with the positive pole of the bat-tery 0 the negative pole of which is connected, through wire 8, contact (2, spring a and wire 10, with the positive pole of the battery 0. N 0 current is therefore normally transmitted upon the artificial line Z.

Assuming the batteries 0 and 0 each to have an eleetro-motive force of one hundred and fifty volts, the batteries 0 and 0 of one hundred volts, and the batteries 0" and 0 of fifty volts, by depressing the keys K and K separately and in combination, currents of the following resultant strengths will be sent to both the main and artificial lines. \Vhen the key K alone is depressed, the connections ofthebatteries O", 0*, O, and 0 will be reversed with reference to the batteries 0' and 0 and the main and artificial linesv The negative pole of the batteries 0 and 0 will be united to the positive pole of the battery 0 through the wire 5, spring I), stop 0, and wire 4, while the positive poles of the batteries 0 and 0 will be united to the negative pole of the battery 0 through wire 6, lever a, lever 70, and wire 3. Each system of connected batteries being 110w included in circuit in the same direction, a positive current from an electro-motive force of three hundred volts will be transmitted to the main line L and an equal negative current to the artificial line Z. \Vhen the key K alone is depressed, the batteries O and 0 only are reversedwith reference to the remaining batteries and the main and artificial lines. The negative pole of the battery 0 is connected, through wire 9, spring I), resting-contact e, and wire 8, with the negative pole of the battery 0*. The positive pole of the battery 0 is at the same time connected, through the wire 10, spring a, lever 7c, and wire 7, with the positive pole of the battery 0. Positive and negative currents corresponding to an electro-motive force of one hundred volts will therefore be transmitted upon the main and artificial lines, respectively, when the key not exceeding one hundred volts.

K alone is depressed. When both keys K and K are simultaneously depressed, the negative and positive poles of the batteries 0 and 0 respectively, will be connected with the like poles of the batteries 0 and 0", respectively, in the same manner as when the key K alone is depressed, except that in the present instance the polarity is reversed. The resultant currents sent to the main and artificial lines will be positive and negative currents, respectively, due to an electro-motive force of two hundred volts. The three classes of currents thus produced may be employed at the receiving-sta tion for actuating two receiving-instruments, one or the other, or both, responding, accordingly as one or the other or both keys are depressed. The apparatus which I prefer to employ for this purpose is illustrated in connection with the transmitting devices shown in Fig. 1, the apparatus at the distant station being precisely similar thereto.

R and R represent the two receiving-instruments, designed, respectively, to respond to currents from electromotive forces of three hundred and one hundred volts, while both respond to currents from an electro-motive force of two hundred volts. In order to effect this result, the receivinginstrument R consists of an ordinary electroanagnet, M, having its respective coils m it included in the circuits of the conductors 1 and 2,1eading from the battery-sections O and 0 to the lines Land 1. The coils in and n are so connected that mag- .netism of like polarity will tend to be induced in the poles of each core when the circuit-connections of the local batteries are completed, and its armature 1'' will therefore not be af fected by the operation of the transmittingkeys at the home station. A tension-spring, i, normally exerts sufficient force upon the armature 1" to prevent it from responding to currents proceeding from the distant station when corresponding to an electro-motive force The ten sion is, however, insufficient to resist the action of alike current corresponding to an elec-' troanotivc force of two hundred or more volts. The receiving-instrument Rtherefore responds to currents transmitted from the distant station by closing the key K, either alone or simultaneously'with the closing of the key K" at the same station.

It is evident that both coils of the electromagnet M might be included in the conductor 13, leading from the junction of the conductors 11 and 12 to the earth; but for the purpose of reducing the resistance of the circuit Iprefer to include it in the circuits of both'the conductors 1 and 2, as described. 6o.

. It is evident, moreover, that, as the receiving-instrument R is designed to respond only to currents of considerable intensity, the magnetism induced by the incoming current while traversing one coil, m, only of the magnet M will be sufficient to serve all the requirements. The receiving-instrument R is preferably in-' cluded in the circuit of the conductor13, leading from the junction of the conductors 11 and 12 to the earth. It consists of a single electro-magnet, M, having two oppositely-polarized armatures, 1" and 1", corresponding, respectively,to its two cores. Two contact-stops, S and S", and two banking-screws, S and S", are respectively provided, against which the armatures r and are thrown when under the magnetic influence of the various changes in the strength of currents traversing the line. Suitable tensionsprings, t and 15 are provided for normally maintaining the armatures r and r in contact, respectively, with the banking screw S and contact-stop S. The armatures 1' and are normally in electrical connection with each other through the conductor n, and the contact-stops S and S are also in electrical connection with each other by means of a conductor, 14, in the circuit of which is included a local battery, 1), and sounder 1). It will now be evident that the sounder p will be actuated whenever the circuit of the battery 12 is completed thcrethrough by the simultaneous contact of the armatures r and 1' with their respective contact-stops S and S.

For the purpose of rendering the instrument R capable of responding tocurrents proceeding from an electro-motive force of one hundred and two hundred volts, but not of three hundred volts, the tension of the retractile spring t is so adjusted that the polarized armature'r, while normally held against the banking-screw S, will respond to an incoming current from an electro-motive force of one hundred volts, and will thereby be thrown against the eontact-stop S. The same current, however, will be insufficient to actuate the armature r hence the circuit of the local battery 1) will be closed and the sounder p actuated. A current corresponding to an electro-motive force of two'hundred volts will also be sufficient to actuate the po larized armature r in the same manner as just described, but will be insut'ficientto actuate the armature r. The sounder 1) will therefore respond to incoming currents, whether from an electro-motive force of one hundred or of two hundred volts. An incoming current from an electro-motive force of three actuating the armature r, besufficient to actuate the armature r against the force of its retractile spring and carry the armature w away from its contactstop S thereby opening the local circuit and causing the sounder p to remain inactive.

' Having thus described the method of trans mitting and receiving the electric currents requisite for simultaneously transmitting two communications in the same direction over a single conductor, it remains to describe the method of applying to the apparatus means for overcoming the detrimental effects due to the difference in the normal potentials'of the transmitting terminals, and consequently in hundred volts will, however, in addition to the corresponding earth-connections of the main and artificial. conductors in which the reeeiving-instruments It and R are included.

it-h an arrangement of apparatus such as illustrated in Fig. 1, wherein the various batteries or battery-sections at any given station oppose and neutralize each other, I prefer to employ a branch line, I, extending around the series of batteriesnormally connected with the artificial line, one extremity of the con-- ductor I being connected with the batteryterminal of the artificial line Z, and the other extremity with the earth-terminal 13 at the junction x of the two conductors 11 and 12.

The resistance of this circuit I should be considerably greater than that of the artificial line including the rheostat X. It may in practice be made two or three times as great with advantage, so that in effect it constitutes a shunt or leak around one section or the other of the main battery, according to the position of the key K. It will then become necessary to increase the resistance X until the joint resistance of the lines 7 and Z is equal to that of the main line L.

It is well knownthat when an electro-magnet or other like electro-magnetic inductor is placed in a circuit its effect is to oppose the initial fiow of the current through its surrounding coil by setting up an opposing electro-motive force, and also to prolong the normal existence of the current, when interrupted, by setting up another electro-motive force, this time in the same direction as the original current. The effect of this action of the inductorl upon the apparatus is as follows: Vhen either or both of the keys K and K are closed, a positive current is sentto the main line L and a nega tive current to the artificial line Z. The immediate tendency of the current transmitted to the main line is to flow into theline with much greater rapidity at first than after the line has become partially or fully charged. The current transmitted to the artificial line I, however, is opposed in that line by a resistance much greater per unit of length, and the initial flow of the current will be proportionately less through that line. Hence the potentials at the battery terminals of the main and artificial lines difier from each other in proportion to the ratios which the rapidities of the flow ol' the currents from those points to line bear to each other. The same difference of potential obviously exists at the opposite terminals of the respective batteries or series of batteries, and this difference in potentials tends to result in an uncompensated efi'ect upon the re cei ving-instruments connected with those poles of the batteries. By properly adjusting the resistance of the branch circuit 1 and the retarding effect produced by the inductor l, the escape or How of the current from the line terminals of each of the batteries or series of batteries may be made practically equal, thereby rendering the potentials at the corresponding terminals of the batteries also equal. The effect produced upon the receiving-instruments 1t and R by each series of batteries will then be entirely neutralized.

\Vhen the keys K and K are operated to reduce or interrupt the flow of current upon the main and artificial lines, the tendency of the artificial line is to discharge instantly, while that of the main line is to discharge more slowly, thereby producing unlike effects upon the receiving-instrunrents R and It. This difference in electrical discharge is compensated for and equalized by the comparatively slow discharge on the part of the inductor I in the branch Z of the artificial line I.

For the purpose of rendering the retarding eliect of theinductor readily adjustable, 1 construct the same in the manner illustrated in Fig. 2, wherein U represents a supporting base, upon which are rigidly mounted the coils w of the inductor and a standard, a. 'lhrough the centers of the coils w w extend cores 1? i, which are eachv constructed of a soft-iron or magnetizable section, 1", and a section, 1*, ol'

non-magnetic material, such as brass. These two sections are united by a long beveled oint, q'f'f, which construction permits of a careful adjustment of the amount of magnetizable metal included within the coils. The respective ex.- tremities of the cores thus formed are secured to two plates, 12 and t, of non-conducting material, and the entire frame thus formed is movable in the direction of the length 01" the cores by an adjusting-screw, V, turning in a suitable threaded hole, a, formed in the standard a, the extremity of the screw being attached to the plate t by a swivel joint, as shown at v.

]'n the drawings I have shown a modification in the method of carrying out my invention which is especially applicable to systems wherein a locally unopposed battery is normally connected with the mainline. Such an arrangement is illustrated in Fig. 3, wherein O and 0" represent two equal sections of a bat tery having its respective poles connected with the main line L and artificial line 7. A conductor, 15, proceeds from a point, 51 in the conductor 16, connecting the two sections to the earth at G. In this conductor is included any suitable form of reeeivinginstrument, It. A polechanging key, K", similarin construction to the key K, described in connection with Fig. 1, is provided for reversing the connections of the battery-sections O and 0" with reference to the main and artificial lines. A branch conductor, Z extends from a point between the key K" and the main line L to the point 9/ in the earth-comluetor. In this branch conductor is included a condenser, 0, having a capacity proportionate to the dill'erence between. the electrostatic capacities of the main and artificial lines L and Z, respectively. The action. ofthis condenser is as follows: \V hen the key K is at rest, the positive pole of the battery-section O" is connected with the main line L and its negative pole with the earth through the conductor 15. Consequently the line, constituting a permanent shunt around condenser C will receive a certain definite charge, dependent upon the electro-motive force of the battery-section O. c The positive and negative poles of the section 0 will at the same time be respectively connected with the earth at G and the artificial lineZ. When the key K is depressed, the battery-connections will be reversed with reference to the main and artificial lines, the negative pole of the sectiono" being now connected with the main line and the positive pole of the section 0 with the artificial line. The immediate result of thus reversing the battery-connections will be to produce a greater fall in potential at the terminals of the section connected with the main line than at the terminals of the section connected with the artificial line, in a manner similar to that described with reference to Fig. 1,. The necessary result of this difference in potentials would be to establish a curv rent through the conductor 15, connected with the earth, producing a corresponding action of the receiving-instrument included therein, The charge previously stored up in the condenser 0, however, enables it toequalize the potentials of the two battery-sections by serving in the capacity of a supplementary battery, it being connected in series with the battery of lower potential-that is to say, the one .which for the time being is connected with-the main line. Thus its electrically positive and negative plates coincide in direction with the corresponding poles of the battery-section. The charge of the condenser will accordingly be added to the current of thebattery-section and willact to maintain the requisite degree of potential. The condenser G will, moreover, immediately receive an opposite charge, which in turn will serve to maintain the potential of the oppositebattery-section when the key K is again reversed.

I claim as my invention 1. The hereinbefore described method of neutralizing at the transmitting-station the electro-staticeffects arising from a difference in the respective electrical capacities of the main and artificial lines of a telegraphic sys tem, which consists in modifying the potential of the battery applied to the artificial line correlatively with the changes in the potential of the battery applied to the main line during the transmission of the signal.

2. The combination, substantially as hereinbefore set forth, with the main and artificial lines of a telegraphic system, of a battery and a branch circuit constituting a permanent shunt around aportion of said battery, having an inductive capacity approximately equal to the difference in the inductive capacities of the main and artificial lines.

3. The combination, substantially as hereinbefore set forth, with the artificial line of a du plex or multiple telegraph, of a battery and a branch circuit connected with said artificial that portion of said battery which is applied to the artificial line.

4. The combination, substantially as hereinbefore set forth, with the artificial line of a din plex or multiple telegraph, of a main battery, a

branch circuit connected with said artifical line and constituting a permanent shunt around the portion of said battery which is applied to the artificial line, and an electromagnetic inductor included in the said branch circuit.

5. The combination, substantially as hereinbefore set forth, with the artificial line of a duplex or multiple telegraph, of a battery, a branch circuit connected with said artificial line and constituting a permanent shunt around a portion of said battery, an electro-magnetic inductor included in said branch circuit, and means for adjusting the energy and duration of the electric discharge from said inductor.

6. The combination, substantially as hereinbefore set forth, with the main and artificial lines of a duplex or multiple telegraph, of two electrically equal and similar series of batteries or battery-sections, means, substantially such as described, for transmitting from said batteries through said main line currents of three different strengths and given polarity, and simultaneously transmitting upon the artificial line currents of equivalent strengths but opposite polarity, and a branch line constituting a shunt around the portion of said battery-sections connected with said artificial line.

7. The combination, substantially as hereinbefore set forth, with the main and artificial lines of a duplex-or multiple telegraph, of two series of battery-sections, the opposite poles of which are respectively connected with said main and artificial lines, each series comprising three sections, the sum of the electro-motive forces of two of said sections being equal and normally opposite to thatof the remaining section, and means, substantially suchas described, for simultaneously interchanging the circuit-connections with reference to the main line of one or both the corresponding lesser battery-sections in each series.

8. The combination, substantially as herein- ALEXANDER MUIRHEAD.

\Vitnesses:

DANIEL W. EDGECOMB,

- CHARLES A. TERRY. 

